KR0143346B1 - Fabrication method of phase shift mask - Google Patents

Abstract

The present invention relates to a method of fabricating a phase inversion mask, wherein the quartz substrate is dry-etched to a certain depth to form a first groove, and a wet groove is used to form an undercut in the first groove and to form a second groove in which the undercut is formed. The chromium pattern acts as a protective film to prevent scattering from the sidewalls of the grooves, thus providing a uniform light intensity profile to form a pattern with a uniform line width on the semiconductor substrate. It is a technology that can improve the reliability of the device.

Description

Phase reversal mask manufacturing method

1A and 1B and FIGS. 2A and 2B are detailed views showing light intensity profiles during a phase shift mask manufacturing process and an exposure process as an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

11: Quartz substrate 13: Chrome pattern

15: first home 17: second home

19: light intensity profile

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a phase shift mask, and more particularly, to a technique of manufacturing a phase shift mask that can be formed with a uniform line width when forming a fine pattern of a semiconductor device.

Conventionally, a lithography process is performed using a mask in which a plurality of chromium patterns are formed. However, in the case of using a mask having such a chromium pattern, the transmitted light is in phase with each other between adjacent patterns, so that the patterns cannot be accurately separated at the pattern boundary, resulting in a poor fine state after the photoresist development, resulting in a resist resist. scum) and a bridge are generated. In order to solve this problem, a phase shift mask is used.

The phase inversion mask minimizes diffraction and interference of light in the central region of the non-exposed area by using the mutual interference action of the transmitted light to increase the resolution by increasing the light contrast relatively in the transmitted area, and increases the process margin. Improve.

On the other hand, the phase inversion mask is classified into a Levenson type, an auxiliary pattern attachment type, a halftone type, and the like according to the structural shape of the mask. And, they are relatively easy to apply depending on the structure of the pattern and the effect of process improvement is great. However, in the ultraviolet (Duv) region having a wavelength of 200 to 300 nm, the energy absorption coefficient due to the phase inversion material is increased and the light is increased. By making it difficult to control the transmittance, there is a problem in that it is impossible to form a fine pattern having a uniform line width on the upper surface of the semiconductor substrate by reducing the phase inversion effect, thereby reducing the reliability of the semiconductor device.

Accordingly, the present invention uses a phase inversion effect using a thickness difference between the quartz substrate and the unetched quartz substrate by etching the quartz substrate in order to solve the problem occurring in the far ultraviolet region when forming the phase inversion mask according to the prior art. It is an object of the present invention to provide a method for manufacturing a phase inversion mask.

In order to achieve the above object, a method of manufacturing a phase inversion mask according to the present invention includes a mask process using a chromium pattern on an upper portion of a quartz substrate to etch the quartz substrate so that an undercut is generated under the chromium pattern. Characterized in that it has a strength profile, the phase inversion mask is a process of depositing a chromium film on a quartz substrate a predetermined thickness, forming a chromium pattern by etching the chromium film using an electron beam, and the chromium pattern Forming a first groove by dry-etching one side of the quartz substrate using a mask as a mask, and isotropically etching the quartz substrate by a predetermined depth by a wet method using the chrome pattern as a mask. Forming a groove and simultaneously forming an undercut in the first groove and the second groove. And it characterized in that.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1A and 1B and FIGS. 2A and 2B are detailed views showing a phase inversion mask manufacturing process and a light intensity profile as an embodiment of the present invention.

FIG. 1A is a cross-sectional view illustrating that the chrome pattern 13 is formed on the quartz substrate 11 on which the predetermined portion of the quartz substrate 11 is etched to form the first groove 15.

Referring to FIG. 1A, a chromium pattern 13 is formed on the quartz substrate 11 to expose a predetermined portion of the quartz substrate 11 by etching the chromium film by an exposure and development process using an electron beam.

At this time, the thickness of a chromium film shall be 800-1200 GPa.

Thereafter, only one side of the quartz substrate 11 is anisotropically etched using the chrome pattern 13 as a mask to form the first groove 15.

At this time, the anisotropic etching is dry etching using fluorine plasma. The depth of the formed first groove 15 is λ / 2 (n −1) (λ: exposure wavelength, n: refraction melting of a quartz substrate), and in this embodiment, it is 2750 750. Thus, the depth of the first groove 15 is 3750 mm by adding about 2750 mm deep of the etched quartz substrate 11 and about 1000 mm thick of the chrome pattern 13. However, when the exposure process is performed in this state, scattering occurs from the sidewall of the first groove 15 to cause a difference in light intensity from the portion where the groove is not formed. Therefore, when the pattern is formed on the semiconductor substrate by using the same, the line widths of the patterns may be different from each other due to the difference in light intensity, and there may be a problem of maintaining the photoresist residue.

FIG. 1B is a detailed view showing a light intensity profile 19 when light is transmitted using a mask in the state of FIG. 1A. FIG. 1B shows light in a portion where the first substrate 15 is formed by etching the quartz substrate 11. It is shown that the intensity is smaller than the light intensity of the portion where the quartz substrate 11 is not etched. Here, the dotted line shows the ideal light intensity profile.

FIG. 2A is a cross-sectional view showing that the first groove 15 is deeper and the second groove 7 is formed using the chrome pattern 13 as a mask after the process of FIG. 1A.

Referring to FIG. 2A, the quartz substrate 11 exposed by the chrome pattern 13 is formed by forming the first groove 15 deeper by etching by Δdx by a wet method using the chrome pattern 13 as a mask. Etching the other side of the) to form a second groove (7).

At this time, in the wet method, the mixing ratio of pure water with the chrome pattern 13 as a mask is 9: 1 B. O. E. (bOE: bufferde Oxide Etchant, hereinafter referred to as bOE) A quartz substrate 11 was etched using 800 to 1200 Å by using a solution.

Accordingly, an isotropic profile is formed in the first groove 15 and the second groove 7 in which an under cut having the chrome pattern 13 as a protective film is formed.

Here, the width of the undercut is determined in consideration of the optical parameters, the size of the line width to be formed, and the amount of focus change. In addition, the undercut increases the light intensity by preventing the chromium pattern 13 from scattering light from the sidewall of the quartz substrate 11 during the exposure process so that there is no difference between adjacent light intensities.

In addition, the wet method is performed by mixing the bOE solution with 7: 1, 9: 1, 50: 1 or 100: 1 pure water in consideration of the etching material and the line width formed.

An embodiment of the present invention is an exposure mask to form a 0.35 μm line and space pattern structure using KrF excimer stepper having a 0.50 Na (Numerical aperture) and a coherence factor of 0.55. It is optimized to form a phase inversion mask.

FIG. 2B is a detailed view simultaneously showing the light intensity profile during the exposure process that transmits light after the FIG. 2A process, showing that the light intensity of the portion where the first groove 15 and the second groove 17 are formed is the same. And the dashed line, i.e., almost coincides with the ideal light intensity profile.

In this case, the light intensity can be determined by determining the width of the undercut, that is, the width of the undercut, according to the optical parameters such as Na and the coherence factor of the projection lens, the size of the line width to be formed, and the amount of focus change. .

According to the present invention described above, stable and uniform light intensity distribution can be obtained by reducing the scattering phenomenon of light by the etched surface of the etched quartz substrate, and a uniform line width is obtained by the same light intensity distribution. In addition, stable process control is possible, and at the same time, generation of photoresist residues can be prevented, thereby improving reliability of the semiconductor device.

Claims (7)

A method of manufacturing a phase shift mask according to claim 1, wherein the quartz substrate is etched to generate undercuts under the chromium pattern by a mask process using a chromium pattern on the top of the quartz substrate. The method of claim 1, wherein the phase inversion mask comprises depositing a chromium film on a quartz substrate, forming a chromium pattern by etching the chromium film using an electron beam, and using the chromium pattern as a mask. Forming a first groove by dry-etching one side of the substrate to a predetermined depth, and forming a second groove on the other side of the quartz substrate by isotropically etching the quartz substrate by a constant depth by a wet method using the chromium pattern as a mask. And a step of forming an undercut in the first groove and the second groove. 3. The method of claim 2, wherein the chromium film is formed to a thickness of 800 to 1200 GPa. The method of claim 2, wherein the dry etching is performed using fluorine plasma. The method of claim 2, wherein the depth of the first groove is lambda / 2 (n -1). The method of claim 2, wherein the wet etching is performed to etch the first groove deeper by Δdx and to form a second groove at a depth of Δdx. The wet etching method of claim 6, wherein the wet etching is performed using a boe solution having a mixing ratio of 7: 1, 9: 1, 50: 1 or 100: 1 in consideration of the etching material and the line width. Phase inversion mask manufacturing method.